L-α-glycerophosphate (αGP), a key constituent in phospholipid metabolism (Kennedy and Weiss, 1956), is abundant in most biological tissues (Dawson, 1958). β-Glycerophosphate (βGP) is a product of enzymatic (Ukita et al., 1955) and alkaline (Clarke and Dawson, 1976) hydrolysis of phospholipids and is formed through the cyclic phosphodiester intermediate 1,2-cyclic glycerophosphate (1,2 cGP) (Ukita et al., 1955; Clarke and Dawson, 1976). 1,2 cGP has been detected in algae species (Boyd et al., 1987) as well as in human cancer tissues (Su et al., 1993). Similarly, αGP can in principle adopt the cyclic form 1,3-cyclic glycerophosphate (1,3 cGP). This compound has been shown to be formed as an intermediate in the phospholipase C hydrolysis of phosphatidyl glycerol (PG) (Shinitzky et al., 1993) and upon further hydrolysis is converted to αGP.
A six-membered cyclic phosphate of foremost biological importance is cyclic AMP. The ring of cyclic AMP is actually a derivative of 1,3 cGP backbone. Other cyclic phosphates which were detected in biological systems include glucose cyclic phosphodiester (Leloir, 1951), 2′,3′-cyclic phosphodiester (Markham and Smith, 1952), riboflavin-4′,5′-cyclic phosphodiester (Forrest and Todd, 1950), myoinositol-1,2-cyclic phosphodiester (Dawson et al., 1971) and cyclic lysophosphatidic acid (Friedman et al., 1996).
Except for cyclic AMP and cyclic GMP which have been extensively studied, no specific biological activities have been so far assigned to the other biological cyclic phosphates.
List of Compounds and Their Abbreviations
The following compounds which formulas are presented in Appendix A just before the claims, will be represented herein in the specification by their abbreviations as follows:    1. 1,3 cyclic glycerophosphate—1,3 cGP    2. 1,2 cyclic glycerophosphate—1,2 cGP    3. 3-acyl 1,2 cyclic glycerophosphate (cyclic lysophosphatidic acid)—c-lysoPA    4. Phenyl 1,3 cGP—P-1,3 cGP    5. Phenyl 1,2 cGP—P-1,2 cGP    6. 1,3 cyclic propanediol phosphate—1,3 cPP    7. 1,2 cyclic propanediol phosphate—1,2 cPP    8. Phenyl 1,3 cPP—P-1,3 cPP    9. Phenyl 1,2, cyclic propanediol phosphate—P-1,2, cPP    10. Cyclic dihydroxyacetone phosphate—cDHAP    11. Phenyl cyclic dihydroxyacetone phosphate—P-cDHAPGlossary
The following is an explanation of some terms used above and in the following description and claims:    CG—the cyclic glycerophosphates and analogs thereof of the invention.    Target cells—cells in which, following contact with the CGs of the invention, there is phosphorylation of intracellular proteins. In some cases, contact of the target cells with CGs results in maturation of the cells and in other cases in hormone-like signaling activities. In addition, a variety of cellular events may occur in the target cells following their contact with the CGs of the invention.    Intracellular phosphorylation (used interchangeably with phosphorylation of intracellular proteins)—rise in the level of phosphorylation in one or more of the intracellular proteins of the target cells following incubation of the cells with the CGs of the invention. The phosphorylation is typically of the tyrosine amino acid in the protein but may also be of the threonine or serine amino acid. The protein may be any protein inside the target cell that can be phosphorylated. Typically the protein in which phosphorylation occurs is constitutively phosphorylated to some extent and the level of its phosphorylation is effected by the CGs. The level of phosphorylation may be determined using any of the methods known in the art such as those described below.
Promotion of cell differentiaton—the activity of the CGs of the invention causing changes in the target cells which are correlated with the differentiation stage of the cells. The changes may be in anatomical characteristics, in the expression of differentiation antigens, etc.    Induction of hormone-like signaling—the activity of the CGs of the invention on target cells which results in changes which are typically induced by hormones. The CGs applied externally to the target cells pass through the cell membrane and exert their effect inside the target cells. For example, in target cells expressing the insulin receptor, such changes may be similar to the effects exerted by insulin on the same cells.    Analog—relates to any compound which is derived from one of the cyclic glycerophosphates of the invention and which substantially maintains the activity of the cyclic glycerophosphate from which it was derived, including, for example, deoxy analogs and phenyl esters of the cyclic glycerophosphates, preferably, deoxy analogs.    Substantially maintaining—this term relates to the analogs ability to promote the activity carried out by the cyclic glycerophosphate from which they were derived to a certain extent. The analog's activity will be considered to be substantially maintained wherein the activity is 30% or above, preferably 50% or above, more preferred 70% or above, and most preferably 90% or above the level of the activity of the cyclic glycerophosphate.    Effective amount—wherein the method of the invention is intended for prevention of a non-desired condition, the term “effective amount” should then be understood as meaning an amount of the active compound which, when administered, results in the prevention of the appearance of the said condition. Prevention of such a condition may be required prior to the appearance of any symptoms of a disease, e.g. in individuals having a high disposition of developing the disease. Wherein the compositions or methods are intended for treatment of an ongoing non-desired condition, the term “therapeutically effective amount” should then be understood as meaning an amount of the active compound which is effective in ameliorating or preventing the enhancement of the treated condition and related symptoms, which reduces the undesired symptoms or which completely eliminates them.